QUOTE(bulitt @ Feb 24 2013, 05:03 AM)
Engine running too lean, Too much, or too little timing advance, broken fan impellers, air flaps as mentioned, wrong spark plugs, mouse nests in tins, too high compression ?
Too lean is hard to manage at 6000'+ unless you work at it.
Hard to imagine broken fan bits in the 911 fan which runs at about 1.7x crankshaft speed.
Spark plugs don't really affect oil temp.
Flaps came in 1973, no original 6's had them.
Same with compression - if it's too high, it's not original ;-) It also falls at altitude.
Debris covering the cylinder and head tops and the oil cooler is a BIG factor.
I've had two factory /6's and never had cooling issues at "energetic highway" speeds or on the track.
It's a PITA to pull the fan shroud and clean out the detritus but other than intake gaskets and such, the materials cost is low, and the benefits high. The air is colder at altitude but it's less dense and doesn't cool as well, in addition to lowering available power.